Beijing's smog comes from coal burning, vehicle exhaust, and dust from surrounding deserts, and it changes dramatically by season

Beijing's smog is not a single problem but a mix of pollution sources that shift throughout the year. The city burns coal for heating and power, millions of vehicles emit exhaust daily, and dust from the Gobi Desert to the north blows into the city, especially in spring. Winter months — November through March — bring the worst air quality because heating demand spikes and cold air traps pollution close to the ground instead of dispersing it upward. Summer and fall typically see clearer skies.

The pollution you see as haze is made up of tiny particles called PM2.5 and PM10, measured in micrograms per cubic meter of air. PM2.5 particles are small enough to enter your lungs and bloodstream, which is why health warnings focus on this measurement. On bad days, visibility can drop to a few hundred meters, and the air takes on a gray or brownish tint.

China's government has implemented restrictions on coal use, factory emissions, and vehicle traffic on high-pollution days, and these measures have reduced the worst episodes since the mid-2010s. However, Beijing still experiences days when the air quality index (AQI) reaches levels considered unhealthy or hazardous, particularly in winter.

Key Takeaways

  • Beijing's smog peaks in winter months when heating demand increases and cold air traps pollutants near the ground.
  • The main sources are coal burning, vehicle exhaust, and dust from nearby deserts, with PM2.5 particles posing the greatest health risk.
  • The Air Quality Index (AQI) is published hourly by Chinese environmental agencies and international monitors, and readings above 150 are considered unhealthy.
  • On high-pollution days, the government restricts factory operations, limits vehicle traffic, and sometimes closes schools or advises people to stay indoors.
  • Real-time air quality data is available through apps, websites, and the U.S. Embassy's monitoring station, which publishes independent readings.

How the Air Quality Index works and what the numbers mean

The AQI is a scale that converts pollution measurements into a single number so you can quickly understand whether the air is safe to breathe. In China, the index runs from 0 to 500+, with different color codes and health categories. An AQI below 50 is considered good; 51 to 100 is moderate; 101 to 150 is lightly polluted; 151 to 200 is moderately polluted; 201 to 300 is heavily polluted; and above 300 is severely polluted.

The Chinese Ministry of Environmental Protection publishes official AQI readings for Beijing and other cities hourly. The U.S. Embassy in Beijing also operates an independent air quality monitor and publishes its own readings, which sometimes differ slightly from the official numbers because they use different measurement methods and locations. Both sources are publicly available online and through mobile apps.

When the AQI reaches 150 or higher, the government typically issues health warnings and may implement emergency measures. At 200 and above, schools may close, construction sites shut down, and factories reduce operations. Residents are advised to wear N95 or KN95 masks outdoors and to limit time outside.

Where to find real-time air quality information

The most direct source is the China National Environmental Monitoring Centre website, which displays the official AQI for Beijing and all other major Chinese cities updated every hour. You can also check the U.S. Embassy Beijing Air Quality Monitor, which publishes independent readings and is accessible without a VPN from outside China.

Several mobile apps provide real-time data, including the official Chinese environmental agency app and third-party apps like AirVisual (now owned by IQAir) and Plume Air Report. These apps show the current AQI, hourly forecasts, and health recommendations based on the pollution level. Many also send notifications when the AQI crosses into unhealthy ranges.

If you live in or plan to visit Beijing, checking the AQI before going outside is a practical habit, especially during winter. An AQI above 150 means you should consider wearing a mask and limiting outdoor activity, particularly for children, older adults, and people with respiratory conditions.

Health effects of Beijing's smog and who is most at risk

Exposure to PM2.5 and other air pollutants can cause when ready symptoms like coughing, throat irritation, and shortness of breath. Long-term exposure increases the risk of heart disease, stroke, lung cancer, and respiratory diseases like asthma and chronic obstructive pulmonary disease (COPD). Studies of Beijing residents have found associations between years of exposure to high pollution and reduced lung function.

Children, older adults, and people with existing heart or lung conditions face higher risk from poor air quality. Pregnant women may also experience adverse effects, including lower birth weight in exposed pregnancies. Even healthy adults can develop symptoms during periods of severe pollution.

On days when the AQI exceeds 150, reducing outdoor time and wearing a properly fitted N95 or KN95 mask when you must go outside can lower your exposure. Staying indoors with windows closed and using an air purifier with a HEPA filter provides additional protection. Indoor air quality can be significantly better than outdoor air, especially if you seal windows and doors during pollution episodes.

Government actions and restrictions during high-pollution episodes

When the AQI reaches certain thresholds, Beijing's government activates an emergency response system with four levels: yellow, orange, red, and black (though black alerts are rare). Each level triggers different restrictions. At the orange level (AQI 201–300), factories reduce production, construction sites may close, and the government may restrict vehicle traffic by limiting which cars can drive based on license plate numbers. At the red level (AQI above 300), schools close, more factories shut down, and vehicle restrictions tighten.

These measures are announced through official channels and media, usually 24 to 48 hours before they take effect. If you work or study in Beijing, your employer or school will typically notify you of closures or work-from-home orders. Public transportation usually continues operating, though with reduced service on some routes.

The restrictions have measurable effects: studies show that vehicle bans and factory closures can reduce the AQI by 20 to 40 points on the day they are implemented. However, they are temporary measures that address the symptom rather than the underlying causes of pollution.

Long-term trends and improvements in Beijing's air quality

Beijing's air quality was at its worst in the early 2010s, when the AQI regularly exceeded 300 during winter months and visibility sometimes dropped below 100 meters. Since then, the government has invested heavily in pollution control: closing or relocating coal-fired power plants, tightening emissions standards for vehicles, and restricting coal use in heating systems. These efforts have produced measurable improvements.

According to data from the China National Environmental Monitoring Centre, the number of days with severe pollution (AQI above 200) in Beijing has declined from over 100 days per year in 2013 to roughly 10 to 20 days per year in recent years. Winter air quality remains worse than other seasons, but the worst episodes are less frequent and less severe than they were a decade ago.

However, progress has plateaued in recent years, and Beijing still experiences unhealthy air quality on a regular basis during winter. Further improvements would require addressing sources outside the city, such as coal burning in neighboring provinces and dust from deserts, which are harder for Beijing's government to control directly.

Protecting yourself during periods of poor air quality

If you spend time in Beijing, especially during winter, having a supply of N95 or KN95 masks is practical. These masks filter out PM2.5 particles when fitted properly — the key is ensuring the mask seals tightly around your nose and mouth with no gaps. Surgical masks and cloth masks do not provide adequate protection against PM2.5.

A portable air purifier with a HEPA filter can improve air quality in your home or office. HEPA filters remove PM2.5 and other small particles, though they do not remove gases like nitrogen dioxide or sulfur dioxide. Running a purifier continuously in your bedroom or main living space can reduce your exposure during sleep and rest periods.

On high-pollution days, limit strenuous outdoor activity, which increases the amount of air you breathe in. Children should avoid outdoor play, and older adults should reduce exercise intensity. Indoor activities, air-conditioned spaces, and staying home are the most effective ways to reduce exposure when the AQI is very high.

Frequently Asked Questions

Is Beijing's smog getting worse or better?

Beijing's air quality has improved significantly since the early 2010s, with fewer days of severe pollution. However, winter air quality remains unhealthy on a regular basis, and progress has slowed in recent years. The city still ranks among China's most polluted cities during winter months.

What is the difference between PM2.5 and PM10?

PM2.5 refers to particles 2.5 micrometers or smaller, which are small enough to enter the lungs and bloodstream. PM10 particles are larger (up to 10 micrometers) and typically lodge in the upper airways. PM2.5 poses greater health risks because of its ability to penetrate deep into the respiratory system.

Do air purifiers actually work against Beijing's smog?

HEPA air purifiers remove PM2.5 and other particles from indoor air, so they do reduce exposure when used in a sealed room. However, they do not remove all pollutants — gases like ozone and nitrogen dioxide pass through HEPA filters. They are most effective when used continuously in bedrooms or main living spaces.

Why is Beijing's smog worse in winter?

Winter brings increased coal burning for heating, and cold air near the ground traps pollutants instead of dispersing them upward. This temperature inversion effect concentrates pollution close to where people breathe. Spring and summer winds also help disperse pollution more effectively than winter conditions.

Can I trust the official Chinese AQI numbers?

The official numbers are based on real measurements from monitoring stations across Beijing, so they reflect actual pollution levels. However, the U.S. Embassy's independent monitor sometimes reports different readings because it uses different equipment and locations. Checking both sources gives you a fuller picture of air quality.